The use of heat shrinkable thermoplastic films as flexible packaging materials for vacuum packaging various foodstuffs including a meat is well-known. Such plastic materials, rials, however, while in general quite successful for packaging meat understandably have difficulties in successfully packaging sharp or bony products. For example, attempts to package bone-in primal cuts of meat usually result in an unsatisfactorily large number of bag failures due to bone punctures. The use of cushioning materials such as paper, paper laminates, wax impregnated cloth, and various types of plastic inserts have proved to be less than totally satisfactory in solving the problem. The preperation of special cuts of meat or close bone trim with removal of offending bones has also been attempted. However, this is at best only a limited solution to the problem since it does not offer the positive protection necessary for a wide variety of commercial bone-in types of meat. Furthermore, removal of the bone is a relatively expensive and time consuming procedure.
Accordingly, it is one object of the present invention to provide a patch material and method for making the patch which will minimize and eliminate the puncturing of flexible, heat shrinkable vacuum bags by sharp bones.
An example of a prior art method of protecting a thermoplastic bag from puncture is shown in U.S. Pat. No. 2,891,870 which issued on Jun. 23, 1959 to Meyer S. Selby et al. In the Selby patent the exposed bone in a bone-in cut of meat is covered with a wax impregnated cloth and thus protected meat is placed in a heat shrinkable plastic bag. Accordingly, it is another object of the present invention to eliminate the necessity for having a separate packaging item such as a wax impregnated cloth which must be carefully positioned over the bone and to provide a protective patch which will not be as sensitive to or dependent upon the position of the bone within a vacuum bag.
Other patents involving a patch for a shrinkable bag are U.S. Pat. Nos. 4,755,403; 4,765,857; and 4,770,731, all to Ferguson. Australian Patent Publication 11228/88, published Aug. 4, 1988, to Mack, Lustig, and Vicik involves a heat-shrinkable plastic film which is a blend of certain amounts of ethylene-vinyl acetate, linear very low density polyethylene, and linear low density polyethylene. This film is used as a guard patch and annealed to a saran barrier bag such as that disclosed in Canadian Patent 982,923, issued Feb. 3, 1976 to Lustig and Anthony. In the United States, saran has lost its trademark status and become generic. It refers to copolymers of vinylidene chloride and a comonomer therefor, such as acrylonitrile, vinyl chloride, or methyl acrylate. It is well known as a barrier to the passage of oxygen. Moreover, a cross-oriented patch material is disclosed in U.S. Pat. No. 4,534,984 to Kuehne. General background information can be found in U.S. Pat. Nos. 4,547,427 and 4,601,930, both Engelsberger, U.S. Pat. No. 4,542,075, Schirmer, Assignor to Grace, and also in U.S. Pat. No. 4,971,845, issued Nov. 20, 1990, Asker and Stroud, assignors to Star Corporation.
Another object of the present invention is to provide a patch for a thermoplastic vacuum bag which is relatively strong and tough and which can be readily adhered to the outer surface of a thermoplastic vacuum bag.
An advantage with the instant invention is that the foamed patch increases the apparent thickness of the patch, vis-a-vis a patch such as that in U.S. Pat. No. 4,755,403, with minimal cost increase since foaming decreases the density of the patch. Moreover, the foamed patch should absorb more energy during impact.
Percentages recited herein are percentages by weight.
These and other objects of the present invention will be more readily understood from the summary of the invention, the drawings, and the description of the preferred embodiment which follow: